1. Field of the Invention
The present invention relates to an ophthalmic apparatus and a storage medium.
2. Description of the Related Art
Non-contact tonometers are typified by the air blowing type tonometer disclosed in U.S. Pat. No. 3,585,849 developed by Bernard Grolman. This tonometer is designed to optically detect the applanation of the cornea of an eye to be examined by blowing air against the cornea from a nozzle 11 mm away from the cornea and calculate an eye pressure value by calibrating the time taken for the applanation using a Goldmann contact tonometer. The eye to be examined does not always remain still, and it is sometimes impossible to obtain an accurate measurement value due to the influences of the fixation disparity immediately before air blowing and eyelashes. According to conventional techniques, a degree of reliability is added to a measurement value based on the analysis information of a corneal deformation signal, or a standard value is calculated by statistically processing measurement values corresponding to a plurality of times of measurement, thereby allowing the examiner to select an accurate measurement value.
Fixation disparity immediately before air blowing, the eyelid, and the eyelashes may lead to inability to detect a corneal deformation signal to cause a measurement error. This makes it necessary to perform measurement again. In some cases, when a measurement error has occurred, the examiner cannot distinguish whether he/she could not perform measurement due to the movement of the eye to be examined or due to blinking of the eye. As a conventional technique, there is known the non-contact tonometer disclosed in Japanese Patent No. 3885015 (patent literature 2) which captures an anterior eye part image immediately before air blowing upon observation of the eye to be examined, and stores the captured image. This invention is configured to store an anterior eye part image immediately before air blowing and display a still image upon detection of a corneal reflection bright spot projected on the cornea of the eye to be examined due to a measurement error to check the influences of the eyelid and eyelashes.
When obtaining average data by performing measurement a plurality of times, the examiner needs to determine whether to finish examination, by counting the number of times of measurement or checking displayed measurement values, thus requiring troublesome operation. As a conventional technique, there is known the ophthalmic apparatus disclosed in Japanese Patent No. 3649839 (patent literature 3) which continues measurement until a valid measurement value is obtained. This invention is configured to inform the examiner when a measurement error has consecutively occurred a predetermined number of times, temporarily suspend the completion of alignment, start measurement after alignment is completed again, and continue measurement until a valid measurement value is obtained, thereby reducing the operation load on the examiner.
In some cases, however, measurement values uniformly vary regardless of achieving high reliability after a plurality of times of measurement. This is because, although corneal deformation signals only slightly differ in shape, the timings of the detection of the maximum values of the corneal deformation signals differ due to the influences of the slight fixation disparity, eyelid, or eyelashes. The examiner cannot determine which measurement value he/she should select, because of the high reliability of each measurement value.
According to patent literature 2 described above, although an anterior eye part image immediately before each measurement is stored, this technique is effective for only a measurement error. That is, when measurement is properly performed, the examiner cannot check fixation disparity. Patent literature 3 describes that a variation in measurement value is set as a measurement end condition, and measurement is continued until the standard deviation from an average value falls within a predetermined range. When using a non-contact tonometer, in particular, blowing air against the eye to be examined becomes burdensome to the object.